For #242, move the updating of the POTD sequence into a new signals module. When photos are deleted from the admin changelist in bulk, the individual delete() functions on the photo objects is not called. However, the post_delete signal is called for each object.

#!/bin/bash

{% for dl in downloads %}
wget -O {{ dl.dest_filename }} http://{{ domain }}{{ MEDIA_URL }}{{ dl.file.name|urlencode }}
{% endfor %}